The last stage of the government's controversial deal to privatise the maintenance of the Tube has been completed.

Responsibility for maintaining and improving two thirds of London Underground has been handed over to the private consortium Metronet.

It has promised to spend £17bn improving the ageing network during its 30-year contract.

But control of the Tube remains in public hands and is expected to pass from London Underground to Mayor of London, Ken Livingstone, within a few months.

Mr Livingstone, who bitterly opposed the part-privatisation of the Tube network on safety grounds, dropped his legal challenge in February in return for control of the network.

Another consortium, Tube Lines, took over responsibility for the Jubilee, Northern and Piccadilly lines in January. It will be spending £4.4bn on improvements over the next seven years.

New trains promised

Metronet will be responsible for upgrading and running the rest of the network and says it will carry out a thorough deep clean on all stations and trains in the first year.

Other pledges include installing new CCTV, public address systems, help points and destination indicators at all its 150 stations.

Within three years they intend to make improvements to over 60 stations, 25 miles of track and 27 District Line trains.

They have also set targets to cut delays on the Bakerloo, Central and Victoria lines.

The completion of the partial privatisation means that it is vital to the interests of every passenger that the Tube is handed over to London immediately

London mayor Ken Livingstone

By 2008, Victoria Line commuters are promised new state-of-the-art trains.

The Metronet consortium is made up of shareholders Atkins, Balfour Beatty, Bombardier, Thames Water and Seeboard which have each provided £70m of equity.

A further £1bn has been raised in bank loans, £1bn in bonds and £600m from the European Investment Bank.

Balfour Beatty chief executive Mike Welton said they would "be able to play a key role in creating a faster, safer, cleaner and more reliable system".

Despite criticism from the mayor and transport unions, the Government has maintained that using a public-private partnership (PPP) deal is the best way of funding improvements to the ageing underground network.

Mr Livingstone said: "The completion of the partial privatisation means that it is vital to the interests of every passenger that the Tube is handed over to London immediately."

He said current management arrangements were unsatisfactory and meant it was impossible to impose long-term control.